In the nano-fabrication industry, metrology is an important issue because it is needed to ensure the correct alignment and patterning of features. Integrating a sensing system which can instantaneously send back the dimensional information about manufactured products can reduce losses and defect rates. However, it is difficult to perform in-line metrology in nano-fabrication systems because it requires not only real-time inspection but also nanoscale resolution of complex features.
Atomic force microscopy (AFM) has high resolution ability (e.g., sub-nm-scale) and is widely utilized in scientific and industrial applications. However, there are two main drawbacks to the use of AFM metrology in in-line manufacturing applications. The first is the low scanning speed of the AFM sensing probe. The second is the time it takes to place and align samples in the AFM (i.e., long set up times). For example, optical systems and technologies are typically used to align samples by determining the location of the AFM sensing probe relative to the sample. As a result, displacements of the AFM sensing probe are limited to on the order of μm to achieve sub-μm precision.